I'd weld a nut on it.

  On 8/14/2021 at 12:41 AM, Zed Head said:

Here's something I tried on a spare tire locking nut that worked.  Find a socket that fits over the nut but has a small gap between it and the nut.  Fill the socket with a ring or blob of SteelStick, press it over the nut and let it cure.  You've just made your own "key".  It is amazingly strong stuff.

https://www.jbweld.com/product/steelstik-epoxy-putty-stick

This will work if you give it time to cure to full hardness.

Are you sure it's not a 10 spline?

https://www.brandsport.com/bmcc-79241-1.html

Or 8...

https://www.brandsport.com/search-results.html?query=+Spline+Lug+nut+key%2C+Wheel+lock+key+&x=91&y=23

Edited August 16, 20213 yr by Zed Head

I think you have received some good suggestions on how to proceed.  It might be time to start trying them out.

Please let us know which method worked for you.  Good luck!

It’s a 9 spline.  I do not have a welder.  It’s not a full spline down the whole length of long lug. It’s smooth like a cone most of the way then tiny grooves at the bottom.  I have hammered a socket on there so bloody hard.  Then tried to hammer the socket wrench. It keeps slipping off as it’s on a smooth lug.  I will try to dremsl flat sides on the end to get an open ended wrench on.  I would just like to find the bloody key.  Not on Amazon or eBay or even in the 16 part key set.    

Can you post a picture from the side?  A person can see the square shapes at the bottom but they don't look very deep.  Sure does look more like a cap on a nut.  Have you tried grabbing it with Vise-grips and pulling it off.

Maybe it's the angle...

but from the photograph, it appears that some one of the splines might be of a differing width.  Especially comparing the ones in the 10 o'clock and 11 o'clock position.  I suspect the manufacturer alternated the position of the narrow and wider splines to create more variation in what key would fit. Consequently, even if you source a key, having it match the correct spline sequence would be a stroke of good luck. 

 

Kind of looks like split steel meant to flare out and grip a nut...

Here 

65083210319__F766BAB6-3F2E-4124-A326-11A5245DA33F.MOV

They probably went out of business because the design worked so well that if you lost the key you were screwed until you could get a new key.

If you had a long drift (aka drift pin) and were handy with it and the end was shaped right you might be able to turn it that way by pounding on a projection.  But, any slips and you're gouging the rim.

https://www.grainger.com/product/4RPL7

Edited August 16, 20213 yr by Zed Head

A longer cheaper one.  The long punch is very useful, I have this set.  I still think the SteelStik has a chance.

https://www.harborfreight.com/12-piece-punch-and-chisel-set-66337.html

Edited August 16, 20213 yr by Zed Head

Do what with chisel? Cut a groove on top of nut and put chisel and hammer to try and spin it??